A data center network has a huge number of servers, and each server may be virtualized into multiple virtual machines (Virtual Machine, VM). In an IP (Internet Protocol, Internet protocol) network environment, each host is allocated a 32-bit IP address. The IP address is a logical address for identifying the host in the Internet range. For a packet to be transmitted on a physical network, a physical address, that is, a MAC (Media Access Control, media access control) address of destination host must be known. This requires a group of services at the network layer to convert the IP address into a corresponding physical address; in an Internet Protocol version 4, IPv4, the group of protocols is an ARP (Address Resolution Protocol, address resolution protocol). Each VM of the data center network sends an ARP packet to broadcast its address information in a layer-2 network or request address information of other hosts. Each switch automatically learns a MAC address after receiving an ARP packet sent by a VM. Thereby, the switch learns MAC address of all VMs in a subnet, and a large MAC table is formed, usually with millions of entries. As a result, the load of a network device is too high, and processing capabilities are insufficient, and therefore limiting the scale of the network.